1. Field
This invention relates generally to semiconductor devices, and more specifically to heat spreaders in semiconductor device packages.
2. Related Art
A heat spreader is usually placed in thermal contact with a die and is used to dissipate heat from the die. A heat spreader typically has high thermal conductivity.
In known devices, a heat spreader is attached to a die with a thermally conductive adhesive material such as conductive paste. However, a maximum heat dissipation from the die by the heat spreader is limited by a thermal conductivity of the adhesive material. The thermal conductivity of typical adhesive material is about 0.5-1.5 W/mK, and the thermal conductivity of a best adhesive material readily available in the industry is about 5-10 W/mK. Adhesive material that has high thermal conductivity is expensive. A thickness of the adhesive material between a die and a heat spreader is typically at least 20μ. As the thickness of the adhesive material increases, thermal performance of a heat spreader becomes worse, due to a relatively low thermal conductivity of the adhesive material. However, dispensing a thin layer of adhesive material, e.g., 10μ or less, may cause a manufacturability issue, and may result in one or more air gaps forming between a die and a heat spreader. This is disadvantageous because the thermal conductivity of air is very low.
With ball grid array packages, known manufacturing methods may cause wire sagging during placement of a heat spreader. Known heat spreader manufacturing processes are costly.